A single mutation in the ?-globin gene results in production of abnormal sickle globin (HbS), leading to sickle cell disease (SCD). HbS polymerizes into rigid fibers under low O2 tension, causing distorted, rigid red cells (known as cell sickling), and leading to abnormal blood rheology, vasooccclusive crisis, and hemolytic anemia etc. Cell sickling can serve as a diagnostic biomarker of SCD and a monitoring biomarker to assess the efficacy of chemotherapy and gene therapies that target HbS and its polymerization, directly and indirectly. We have recently developed a microfluidics-based hypoxia chip to process small volume of blood specimens (~ few ?L) and induce cell sickling in vitro rapidly (~ few min) by subjecting red blood cells to low O2 tension. Assessment of cell sickling is achieved label-free, using cell-imaging or electrical impedance-based methods. In the conceptualization project, we will study assay sensitivity using spiked leukoreduced homozygous sickle cell samples. In the next stage, we will validate both in vitro assays using homozygous and heterozygous samples, establish relevant operating standards, and automate data processing and analysis. The project will result in validated in vitro assays for rapid, label-free measurement of cell sickling to assess patient response to gene-therapy treatments and other treatments targeting HbS polymerization in general.